Method for controlling the rotational speed or the torque of a motor, rotational speed control system and control device

Abstract

A method for controlling the rotational speed or the torque of a motor to protect a suppressor diode in a control device of a vehicle, wherein the suppressor diode converts recuperation energy of the motor into thermal energy comprises determining the current junction temperature and/or diode voltage of the suppressor diode; and controlling the rotational speed or the torque of the motor by means of the current junction temperature and/or diode voltage in such a way that the junction temperature of the suppressor diode does not exceed a predetermined junction temperature limit value.

1 . A method for controlling the rotational speed or the torque of a motor in order to protect a suppressor diode in a control device of a vehicle, wherein the suppressor diode converts recuperation energy of the motor into thermal energy, comprising:
 determining one of a current junction temperature and a diode voltage of the suppressor diode;   controlling one of the rotational speed and the torque of the motor by one of the current junction temperature and the diode voltage such that the junction temperature of the suppressor diode does not exceed a predetermined junction temperature limit value.   
     
     
         2 . The method as claimed in  claim 1 , further comprising using derating information and storing a dependence between the junction temperature or diode voltage and a power factor in the derating information. 
     
     
         3 . The method as claimed in  claim 1 , further comprising using a current recuperation power. 
     
     
         4 . The method as claimed in  claim 1 , further comprising:
 measuring the current diode voltage;   determining a current recuperation power of the motor;   determining a power factor using the diode voltage and derating information;   determining a target power by multiplying the power factor by a current recuperation power;   determining a speed limit value by using the target power; and   limiting the rotational speed of the motor on the basis of the speed limit value.   
     
     
         5 . The method as claimed in  claim 1 , further comprising determining whether the suppressor diode is conductive, and wherein the method is carried out only if the suppressor diode is conductive. 
     
     
         6 . The method as claimed in  claim 1 , further comprising converting the recuperation energy into thermal energy with the motor. 
     
     
         7 . The method as claimed in  claim 1 , further comprising calibrating the suppressor diode by:
 energizing the suppressor diode with a current in the reverse direction of the suppressor diode;   measuring the diode voltage; and   measuring the junction temperature.   
     
     
         8 . The method as claimed in  claim 7 , further comprising carrying out the calibration as a regular recalibration. 
     
     
         9 . A rotational speed control system for performing the method comprising:
 a control loop; and   a computing unit, wherein the computing unit has instructions for;
 determining one of a current junction temperature and a diode voltage of a suppressor diode; and 
 controlling one of a rotational speed and a torque of a motor by one of the current junction temperature and the diode voltage such that a junction temperature of the suppressor diode does not exceed a predetermined junction temperature limit value. 
   
     
     
         10 . The system as claimed in  claim 9 , wherein a dependence between the junction temperature or diode voltage and a power factor is stored in derating information. 
     
     
         11 . The system as claimed in  claim 10 , further comprising instructions for:
 measuring the current diode voltage;   determining a current recuperation power of the motor;   determining a power factor using the diode voltage and the derating information;   determining a target power by multiplying the power factor by a current recuperation power;   determining a speed limit value by means of the target power; and   limiting the rotational speed of the motor on the basis of the speed limit value.   
     
     
         12 . The system as claimed in  claim 9 , wherein the computing unit carries out the instructions only if the suppressor diode is conductive. 
     
     
         13 . The system as claimed in  claim 9 , wherein the motor convers the recuperation energy into thermal energy. 
     
     
         14 . The system as claimed in  claim 9 , further comprising instructions for calibrating the suppressor diode by:
 energizing the suppressor diode with a current in the reverse direction of the suppressor diode;   measuring the diode voltage; and   measuring the junction temperature.   
     
     
         15 . The system as claimed in  claim 15 , wherein the calibration is carried out as a regular recalibration. 
     
     
         16 . The system as claimed in  claim 9 , wherein the control loop and the computing unit are part of a control device for a vehicle with a rotational speed control system. 
     
     
         17 . A rotational speed control system comprising:
 a motor,   a suppressor diode for a control device of a vehicle, wherein the suppressor diode converts recuperation energy of the motor into thermal energy, and wherein the suppressor diode has a predetermined junction temperature limit value; and   wherein one of the rotational speed and the torque of the motor are controlled by one of a current junction temperature and a diode voltage to protect the suppressor diode such that the junction temperature of the suppressor diode does not exceed the predetermined junction temperature limit value.   
     
     
         18 . The system as claimed in  claim 17 , wherein a speed limit value of the motor is determined based on a target power, wherein the target power is a multiplication of a power factor and a current recuperation power, and wherein the power is dependent on the junction temperature or the diode voltage 
     
     
         19 . The system as claimed in  claim 17 , wherein one of the rotational speed and the torque of the motor are only controlled to not exceed the predetermined junction temperature limit value when the suppressor diode is conductive. 
     
     
         20 . The system as claimed in  claim 17 , wherein the suppressor diode is regularly calibrated, and wherein the calibration includes a measurement of the diode voltage and the junction temperature when the suppressor diode is energized with a current in the reverse direction.